This invention relates to an apparatus and test probe for integrated circuit devices and methods of use thereof.
In the microelectronics industry, before integrated circuit (IC) chips are packaged in an electronic component, such as a computer, they are tested. Testing is essential to determine whether the integrated circuit""s electrical characteristics conform to the specifications to which they were designed to ensure that electronic component performs the function for which it was designed.
Testing is an expensive part of the fabrication process of contemporary computing systems. The functionality of every I/O for contemporary integrated circuit must be tested since a failure to achieve the design specification at a single I/O can render an integrated circuit unusable for a specific application. The testing is commonly done both at room temperature and at elevated temperatures to test functionality and at elevated temperatures with forced voltages and currents to burn the chips in and to test the reliability of the integrated circuit to screen out early failures.
Contemporary probes for integrated circuits are expensive to fabricate and are easily damaged. Contemporary test probes are typically fabricated on a support substrate from groups of elongated metal conductors which fan inwardly towards a central location where each conductor has an end which corresponds to a contact location on the integrated circuit chip to be tested. The metal conductors generally cantilever over an aperture in the support substrate. The wires are generally fragile and easily damage and are easily displaceable from the predetermined positions corresponding to the design positions of the contact locations on the integrated circuit being tested. These probes last only a certain number of testing operations, after which they must be replaced by an expensive replacement or reworked to recondition the probes.
FIG. 1 shows a side cross-sectional view of a prior art probe assembly 2 for probing integrated circuit chip 4 which is disposed on surface 6 of support member 8 for integrated circuit chip 4. Probe assembly 2 consists of a dielectric substrate 10 having a central aperture 12 therethrough. On surface 14 of substrate 10 there are disposed a plurality of electrically conducting beams which extend toward edge 18 of aperture 12. Conductors 16 have ends 20 which bend downwardly in a direction generally perpendicular to the plane of surface 14 of substrate 10. Tips 22 of downwardly projecting electrically conducting ends 20 are disposed in electrical contact with contact locations 24 on surface 25 of integrated circuit chip 4. Coaxial cables 26 bring electrical signals, power and ground through electrical connectors 28 at periphery 30 of substrate 10. Structure 2 of FIG. 1 has the disadvantage of being expensive to fabricate and of having fragile inner ends 20 of electrical conductors 16. Ends 20 are easily damaged through use in probing electronic devices. Since the probe 2 is expensive to fabricate, replacement adds a substantial cost to the testing of integrated circuit devices. Conductors 16 were generally made of a high strength metal such as tungsten to resist damage from use. Tungsten has an undesirably high resistivity.
It is an object of the present invention to provide an improved high density test probe, test apparatus and method of use thereof:
It is another object of the present invention to provide an improved test probe for testing and burning-in integrated circuits.
It is another object of the present invention to provide an improved test probe and apparatus for testing integrated circuits in wafer form and as discrete integrated circuit chips.
It is an additional object of the present invention to provide probes having contacts which can be designed for high performance functional testing and for high temperature burn in applications.
It is yet another object of the present invention to provide probes having contacts which can be reworked several times by resurfacing some of the materials used to fabricate the probe of the present invention.
It is a further object of the present invention to provide an improved test probe having a probe tip member containing a plurality of elongated conductors each ball bonded to electrical contact locations on space transformation substrate.
A broad aspect of the present invention is a test probe having a plurality of electrically conducting elongated members embedded in a material. One end of each conductor is arranged for alignment with contact locations on a workpiece to be tested.
In a more particular aspect of the present invention, the other end of the elongated conductors are electrically connected to contact locations on the surface of a fan-out substrate. The fan-out substrate provides space transformation of the closely spaced electrical contacts on the first side of the fan-out substrate. Contact locations having a larger spacing are on a second side of the fan out substrate.
In yet another more particular aspect of the present invention, pins are electrically connected to the contact locations on the second surface of the fan out substrate.
In another more particular aspect of the present invention, the plurality of pins on the second surface of the fan-out substrate are inserted into a socket on a second fan-out substrate. The first and second space transformation substrates provide fan out from the fine pitch of the integrated circuit I/O to a larger pitch of electrical contacts for providing signal, power and ground to the workpiece to be tested.
In another more particular aspect of the present invention, the pin and socket assembly is replaced by an interposer containing a plurality of elongated electrical connectors embedded in a layer of material which is squeezed between contact locations on the first fan-out substrate and contact locations on the second fan-out substrate.
In another more particular aspect of the present invention, the test probe is part of a test apparatus and test tool.
Another broad aspect of the present invention is a method of fabricating the probe tip of the probe according to the present invention wherein a plurality of elongated conductors are bonded to contact locations on a substrate surface and project away therefrom.
In a more particular aspect of the method according to the present invention, the elongated conductors are wire bonded to contact locations on the substrate surface. The wires project preferably at a nonorthogonal angle from the contact locations.
In another more particular aspect of the method of the present invention, the wires are bonded to the contact locations on the substrate are embedded in a elastomeric material to form a probe tip for the structure of the present invention.
In another more particular aspect of the present invention, the elongated conductors are embedded in an elastomeric material.